1. Field of the Invention
The invention relates to an apparatus for concentrating radiant energy such as solar radiation, collected over a large area into a smaller area for more efficient conversion of the radiant energy to a more useful form of energy. More particularly, it relates to the use of fluorescent material in a thin film form which is optically bonded by an adhesive to a massive slab of transparent material such as glass or plastic. The incident solar radiation is absorbed by the fluorescent material and re-emitted within the slab to be trapped by the phenomenon of total internal reflection and transmitted to the edges of the slab where it escapes to impinge upon an energy conversion device.
2. Description of the Prior Art
The use of solar energy as a power source has not been cost-competitive with other power-generating methods because of the high cost of solar cells and other solar energy concentrators. It is this prohibitively high cost that has made the typical "flat-array" or non-focusing solar generator impractical even though it has the advantages of being simple and reliable.
In an attempt to lower costs by reducing the cell area, reflective or refractive optics have been employed to concentrate the sunlight falling on a relatively large area of the optics into a smaller area where fewer cells may convert the concentrated radiant energy. However, collectors which re-direct sunlight by focusing require either that they be moved to accurately track the sun's apparent motion, or that they be designed for and positioned at some comprise fixed position. In addition, collectors of this type are not effective to collect diffused radiation encountered when skies are overcast or hazy.
Use of a fluorescent concentrator of the type disclosed in Volume 129 of Research Disclosure published January, 1975 combines the advantages of both types of converters. One disclosed arrangement comprises a multilayer structure wherein a chamber containing fluorescent dyes is formed by two sheets of highly transparent glass with layers between the glass being separated by a pair of transparent spacers. A first dye solution is contained in the chamber formed by the transparent spacers. A second dye solution is contained in each of the upper and lower chambers formed between one of the glass plates and one of the transparent spacers. The fluorescent dye materials are chosen so that the second dye material absorbs the fluorescence of the first dye. The dye solutions in each of the chambers may be replenished and removed via a system of conduits so that any dye solution may be flushed and replaced without disassembly of the cell when deterioration of the dye is observed. Sunlight that penetrates the glass sheets is absorbed by the fluorescent dye and re-emitted. A large percentage of the re-emitted light piped to the edge of the collector where it impinges on an energy conversion device.